1. Field of the Invention
The present invention relates to a light emitting device, and in particular, to a light emitting device having a circuit protection unit.
2. Description of the Related Art
The light emitting device is widely used in some applications, for example, it can be used in optical displays, laser diodes, traffic signals, data storage devices, communication devices, illumination devices, and medical equipment. In this field, in order to improve the yield rate of the light emitting diodes, the prevention of electrostatic damages to light emitting devices is nowadays an important task to technical personnel.
As shown in FIG. 1, in order to prevent a conventional light emitting device from electrostatic damage, the light emitting diode reversely parallel connects with a circuit protection unit such as a Zener diode 50 during the packaging process. As a result, static electricity is released by the Zener diode 50, thereby preventing damage to light emitting device. However, the circuit protection unit is electrically connected with the light emitting device during the packaging process, i.e., the light emitting device is not protected by the circuit protection unit before the packaging process. Specifically, the light emitting device is not protected by the circuit protection unit adequately during the chip manufacturing process of the light emitting device. Moreover, the light emitting device packaging process described above is complex and the manufacturing cost is high.
As shown in US Patent Publication No. 20020179941, a light emitting device with protection against electrostatic damage is disclosed. As shown in FIG. 2, a shunt diode with a doped-silicon base is electrically connected with a light emitting diode. During electrostatic discharging, the discharge current is conducted by the shunt diode with a doped-silicon base, and thus the discharge current is prevented from passing through the light emitting diode. Because the light emitting diode chip is soldered with the shunt diode after dicing, the damage caused by electrostatic discharge during the manufacturing of the light emitting diode is still unavoidable. Furthermore, the manufacturing process requires an additional procedure for soldering the light emitting diode with the shunt diode, thus incurring a relatively high cost.
As shown in U.S. Pat. No. 6,023,076, a nitride-based light emitting diode is disclosed. The first electrode of the light emitting diode is connected to the first semiconductor layer and the second semiconductor layer. A Schottky contact is formed between the first electrode and the second semiconductor layer. When a reverse current occurs, the current is directed from the first electrode to the second semiconductor layer and towards the second electrode, rather than passing through the light emitting diode, so as to prevent damage. The second semiconductor layer is used as a channel to conduct the reverse current. Therefore, the reverse current may pass through the light emitting diode directly and the light emitting diode is damaged when the reverse current becomes excessive.